1. Field of the Invention
The present invention relates to an apparatus for opening and closing a top board of a grand piano.
2. Description of Related Art
As shown in FIG. 9, there has been conventionally known an apparatus for opening and closing a top board of a grand piano. In this apparatus, a top board xe2x80x9caxe2x80x9d of the grand piano is hingedly or pivotally supported along one side of the top board which is on an outer rim b on the side of low-pitched sound keys (i.e., on the left side as seen from a piano player) by means of top hinges c. When the top board is opened, that side of the top board xe2x80x9caxe2x80x9d which lies on the side of the high-pitched sound keys (i.e., on the right side as seen from the piano player) is lifted by hands and is kept in the lifted position by supporting it with a top board prop d. On an inner surface or a lower surface of the top board xe2x80x9caxe2x80x9d, there are provided top board stick cups e so that the front end of the top board prop d can be engaged into one of the top board stick cups e to thereby safely keep the top board xe2x80x9caxe2x80x9d in an open state.
The top board xe2x80x9caxe2x80x9d of the grand piano ordinarily weighs as much as 40 to 50 kgs. Therefore, a piano player who is not strong enough to manually lift it up cannot safely open it. Should his or her fingers or hands slip off the top board xe2x80x9caxe2x80x9d by mistake, the open end of the top board xe2x80x9caxe2x80x9d suddenly and unexpectedly drops onto the outer rim b, which is to be avoided from the viewpoint of safety. In order to avoid such a sudden and unexpected dropping of the top board xe2x80x9caxe2x80x9d, there has been disclosed the following apparatus in Published Unexamined Japanese Patent Application No. 146534/1997. Namely, a rotary type of damper is attached to an outer rim. A force of rotation is given by a coil spring to an axis of rotation of the damper. An arm which is connected to a rotary shaft of the damper supports the top board. By means of the rotary force of the coil spring, an auxiliary force to assist the opening motion is given at the time of opening the top board. At the same time, the dropping energy of the top board is absorbed by the rotary force and the dampening function of the damper. In Published Unexamined Japanese Patent Application No. 231861/1999, there is disclosed the following apparatus. Namely, a cylinder filled with a pressurized gas gives an auxiliary force at the time of opening the top board. When the top board is closed, a damping device absorbs or buffers the shocks at the time of closing the top board.
In the above-described conventional apparatus in which the damper is used, there is an advantage in that a special control apparatus is not required for operating the damper. However, in order to firmly fix the damper to the grand piano, the position of fixing the damper is naturally limited to the outer rim. If that arm of the damper which extends therefrom is short in length, there will be operated on the top hinges a large moment of rotation of the top board which is rotated or swung about the top hinges. As a result, the outer rim is likely to be damaged. If the length of the arm is long, on the other hand, the force of rotation to be operated on the rotary shaft of the damper also becomes large. Therefore, the damper itself and the coil spring must be made large in size, resulting in a poor aesthetic appearance of the grand piano. In addition, there is a disadvantage in that the damper becomes complicated in construction and expensive in cost.
On the other hand, in the above-described conventional apparatus in which is used the cylinder filled with a pressurized gas, the top board is arranged to be closed due to its own weight. The braking or restriction of the falling top board is attained by providing a damping device, and no particular measure is taken to positively prevent the top board from dropping.
Furthermore, in any of the above-described conventional apparatuses, the top board must be opened and closed by manually or personally holding the top board with hands of the piano player. This operation is troublesome.
In view of the above points, the present invention has an object of providing that apparatus for opening and closing a top board of a grand piano which can be easily mounted on the grand piano in a small space for installation and which is inexpensive in manufacturing and does not impair the aesthetic appearance of the grand piano.
In order to attain the above and other objects, the present invention is an apparatus for opening an closing a top board of a grand piano. The top board is hingedly supported along one side thereof on an outer rim of the grand piano. The apparatus comprises a gear-type of jack made up of: a jack main body fixed to a constituting member of the grand piano; and a rod which is movable in a longitudinal direction through the jack main body and which supports the top board in a manner to open and close the top board.
Preferably, an upper end of the rod is in slidable contact with the top board so as to be slidable along an inner surface of the top board.
The apparatus may further comprises a link disposed between the upper end of the rod and the top board, and the link is pivotally supported at the upper end of the rod and at the top board. The link may comprise a first link element one end of which is pivotally coupled to an inner surface of the top board, and a second link element one end of which is pivotally coupled to the constituting member and an opposite end of which is pivotally coupled to an opposite end of the first link element. The upper end of the rod is coupled to the second link in a manner to swing the second link.
A driving shaft for driving the gear-type of jack may be coupled to a handle which is disposed under a key bed or to an electric motor which is coupled to a driving shaft for driving the gear-type of jack in one and opposite directions of rotation.
The rod may have a threaded portion, and a worm wheel in gearing mesh with the threaded portion is meshed with a worm formed on the driving shaft.
According to the above-described arrangement of the present invention, by hingedly supporting the top board by means of the rod of the gear-type of jack, the top board can be opened and closed by a small stroke of the rod. In addition, by coupling the driving shaft of the gear-type of jack to the handle or to the electric motor, and rotating the driving shaft in the normal and the opposite directions of rotation, the opening and closing of the top board becomes easy. Further, since the rod has a threaded portion and the worm wheel in gearing mesh with the threaded portion is meshed with a worm formed on the driving shaft, the position of the top board can be arbitrarily selected and immovably fixed thereto.